William J. Orts

Effect of fiber treatments on tensile and thermal properties of starch/ethylene vinyl alcohol copolymers/coir biocomposites.

Coir fibers received three treatments, namely washing with water, alkali treatment (mercerization) and bleaching. Treated fibers were incorporated in starch/ethylene vinyl alcohol copolymers (EVOH) blends. Mechanical and thermal properties of starch/EVOH/coir biocomposites were evaluated. Fiber morphology and the fiber/matrix interface were further characterized by scanning electron microscopy (SEM). All treatments produced surface modifications and improved the thermal stability of the fibers and consequently of the composites. The best results were obtained for mercerized fibers where the tensile strength was increased by about 53% as compared to the composites with untreated fibers, and about 33.3% as compared to the composites without fibers. The mercerization improved fiber-matrix adhesion, allowing an efficient stress transfer from the matrix to the fibers. The increased adhesion between fiber and matrix was also observed by SEM. Treatment with water also improved values of Youngs modulus which were increased by about 75% as compared to the blends without the fibers. Thus, starch/EVOH blends reinforced with the treated fibers exhibited superior properties than neat starch/EVOH.

Starch, fiber and CaCO3 effects on the physical properties of foams made by a baking process

Abstract Single-use food containers with a self-closing hinged lid made of extruded polystyrene (EPS) or coated paperboard (PB) are used to serve a variety of food products. Food containers made of materials that are inexpensive and can be composted into a useful mulch would be of commercial interest as a replacement for EPS or PB. In this report, a baking process was used to study the functional properties of foams made of starch or starch composites containing fiber and/or CaCO3. Baked foams made of formulations containing only starch had a lower flexural strain to break (eb) and elongation to break (Elmax) than EPS or PB foams. The eb was increased by lowering the starch concentration in the formulations, using potato starch versus wheat, corn or tapioca starch and by increasing the moisture content. Nevertheless, the eb and Elmax values remained lower than in the EPS and PB samples. Calcium carbonate did not improve the mechanical properties of the foams. Foams containing starch and CaCO3 were more dense with lower eb and Elmax compared to foams containing only starch. Foam density decreased and eb markedly increased by including softwood fiber in the dough formulations. Formulations with a starch/fiber ratio of approximately 5:1 or less made baked foams with eb values greater than 5% and Elmax values nearly double those of foams containing only starch. The addition of CaCO3 to starch/fiber foam composites did not improve foam properties. The CaCO3 increased density and decreased eb and Elmax values compared to foams made of starch and fiber.

Biopolymer additives to reduce erosion-induced soil losses during irrigation

Abstract A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more than 80%. None of these biopolymers, however, exhibited the >90% runoff sediment reduction shown by the present industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow, with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to >2.5mM. Calcium improved the sedimentation of the polyelectrolytic polymers in this study.

Encapsulation of Plant Oils in Porous Starch Microspheres

Natural plant products such as essential oils have gained interest for use in pest control in place of synthetic pesticides because of their low environmental impact. Essential oils can be effective in controlling parasitic mites that infest honeybee colonies, but effective encapsulants are needed to provide a sustained and targeted delivery that minimizes the amount of active ingredient used. The present study reports the encapsulation of essential oils in porous microspheres that are within the size range of pollen grains and can be easily dispersed. The microspheres were made by pumping an 8% aqueous high-amylose starch gelatinous melt through an atomizing nozzle. The atomized starch droplets were air-classified into two fractions and collected in ethanol. The size range for each fraction was measured using a particle size analyzer. The mean particle size for the largest fraction was approximately 100 microm with a range from 5 microm to over 300 microm. Part of the reason for the large particle size was attributed to the merging of smaller particles that impinged upon each other before they solidified. The smaller fraction of spheres had a mean particle size of approximately 5 microm. The starch-based porous microspheres were loaded with 16.7% (w/w) essential oils including thymol (5-methyl-2-isopropylphenol), clove, origanum, and camphor white oil. The essential oils appeared to be largely sequestered within the pore structure, since the spheres remained a free-flowing powder and exhibited little if any agglomeration in spite of the high loading rate. Furthermore, SEM micrographs verified that the pore structure was stable, as evidenced by the persistence of pores in spheres that had first been loaded with essential oils and then had the oil removed by solvent extraction. Thermal gravimetric analyses were consistent with a loading rate at predicted levels.

Properties of starch-based foam formed by compression/explosion processing

Abstract Single-use foam packaging is used by manufacturers to protect and preserve a wide array of food and industrial products. Starch is one possible alternative material for making foam products. Starch-based foam was made using a compression/explosion process to study its properties and potential for single-use packaging. A feedstock was first prepared which consisted of wheat (WS), corn (CS) or potato starch (PS) that was formed into aggregates (1–3 mm) and conditioned to moisture levels ranging from 8 to 20%. The conditioned aggregates were loaded in an aluminum compression mold heated to 230°C and compressed for 10 s with 3.5 MPa force. The force was instantaneously released resulting in an explosive release of steam as the starch feedstock expanded and filled the mold. The moisture content of the feedstock influenced the density and compressive properties of the foam. Wheat, corn and potato starch feedstock with 17, 17 and 14% moisture content, respectively, produced foam with some physical and mechanical properties similar to those of commercial food containers. The starch foam had the general shape of the mold and appeared similar to polystyrene. The microstructure of the foam revealed a cellular structure with mostly closed cells less than 1 mm in diameter. However, some regions of the foam had a microstructure similar to that of expanded polystyrene except that the cells were much smaller (

Agricultural chemistry and bioenergy

Renewed interest in converting biomass to biofuels such as ethanol, other forms of bioenergy, and bioenergy byproducts or coproducts of commercial value opens opportunities for chemists, including agricultural chemists and related disciplines. Applications include feedstock characterization and quantification of structural changes resulting from genetic modification and of the intermediates formed during enzymatic and chemical processing; development of improved processes for utilizing chemical coproducts such as lactic acid and glycerol; development of alternative biofuels such as methanol, butanol, and hydrogen; and ways to reduce greenhouse gas emission and/or use carbon dioxide beneficially. Chemists will also be heavily involved in detailing the phytochemical composition of alternative energy crops and genetically improved crops. A resurgence of demand for agricultural chemistry and related disciplines argues for increasing output through targeted programs and on-the-job training.

Effects of processing conditions on nanoclay dispersion in starch-clay nanocomposites

ABSTRACT Wheat starch samples containing Cloisite Na+ and 30B nanoclays were extruded from a twin-screw extruder. Moisture content, temperature, and screw speed were varied to determine their effect on nanoclay dispersion. X-ray diffraction and transmission electron microscopy (TEM) were used to examine nanoclay intercalation and exfoliation. Moisture content had the largest effect on Cloisite Na+ dispersion, with the highest moisture sample containing exfoliated nanoclays. Meanwhile, temperature and screw speed had little effect on Cloisite Na+ dispersion. For Cloisite 30B samples, only an increase in temperature produced slight intercalation of nanoclays. This was due to the incompatibility of starch with the more hydrophobic Cloisite 30B. Also, Cloisite Na+ and 30B intercalation did not depend on specific mechanical energy. In addition, water absorbance tests indicated the Cloisite Na+ sample containing the most well-dispersed nanoclays had the lowest water uptake.

Structural and Morphological Characterization of Micro and Nanofibers Produced by Electrospinning and Solution Blow Spinning: A Comparative Study

Nonwoven mats of poly(lactic acid) (PLA), poly(ethylene oxide) (PEO), and poly(e-caprolactone) (PCL) were prepared at a nano- and submicron scale by solution blow spinning (SBS) and electrospinning in order to compare crystalline structure and morphology developed by both processes during fiber formation. Polymer solutions were characterized by rheometry and tensiometry. Spun fibers were characterized by several analytical steps. SEM analyses showed that both solution blow spun and electrospun fibers had similar morphology. Absence of residual solvents and characteristic infrared bands in the solution blow spun fibers for PLA, PCL, and PEO was confirmed by FTIR studies. XRD diffraction patterns for solution blow spun and electrospun mats revealed some differences related to distinct mechanisms of fiber formation developed by each process. Significant differences in thermal behavior by DSC were observed between cast films of PLA, PCL, and PEO and their corresponding spun nanofibers. Furthermore, the average contact angles for spun PLA and PCL were higher than for electrospun mats, whereas it was slightly lower for PEO. When comparing electrospun and solution blow spun fibers, it was possible to verify that fiber morphology and physical properties depended both on the spinning technique and type of polymer.

Preparation and characterization of novel micro- and nanocomposite hydrogels containing cellulosic fibrils.

The main objective of this article was to report a simple, fast, and low cost strategy for the synthesis of micro- and nanocomposites by adding cellulose nanofibers, obtained by acid hydrolysis, and added to hydrogels as reinforcing agents. Specifically, when cellulose nanofibers were added to hydrogels, morphologic analyses showed significant decreases in pore size and formation of three-dimensional well-oriented porous microstructure. It was also observed that cellulose nanoparticles improved the mechanical and structural network properties without negatively impacting their thermal and hydrophilic properties. The value of maximum compressive stress was 2.1 kPa for the PAAm-MC, and it increased to 4.4 kPa when the cellulose nanofiber was incorporated into the hydrogel. By investigation of XRD patterns, it was found that the incorporation of cellulose nanofiber affected the crystallinity of PAAm-MC hydrogels, thus contributing to improvements in mechanical, structural, and hydrophilic properties of the PAAm-MC hydrogels.

In situ laminating process for baked starch-based foams

Abstract Single-use foam packaging made of extruded polystyrene (EPS) or coated paperboard (PB) is used for numerous food and beverage products. Considerable commercial interest is focused in developing new technologies for making single-use food containers that are partially or totally degradable in composting facilities. Wide interest has developed in a baking technology for making starch-based food containers with a hinged lid that appear similar to clamshell containers made of EPS. However, the starch-based food containers are brittle and moisture sensitive and must be coated after baking to provide an adequate moisture barrier. The present study describes an in situ method of baking and laminating the starch-based foams in a single step. The procedure involves a dough formulation consisting of starch, fiber and magnesium stearate that is placed in a mold-heated to 160°C between two sheets of laminate. Sheets of laminate material tested included foil, tissue paper, weighing paper, polyvinyl alcohol film and polyvinyl chloride film. The laminated foams generally had a higher density, tensile strength, elongation to break and flexural strength than the non-laminated sample. All of the laminate materials decreased the water vapor permeance. Foam samples laminated with foil, polyvinyl alcohol (PVOH, processed at 130°C) or polyvinyl chloride sheets had the lowest permeance values and had mechanical properties in the same range as those of commercial containers made of EPS or coated paperboard.